This is actually not surprising in the sense that one would expect technological progress among chimpanzees to be quite slow, given that they are less intelligent than humans. So it's logical that their tool-using techniques have not changed much in millennia.
One point the article gets slightly wrong is that the using of tools, as such, is not what is unusual about chimpanzees. Several animal species, some of them not even primates, use tools. What had been claimed to be unique to humans was making tools. This claim was exploded by Jane Goodall's field studies, which found that chimpanzees sometimes strip the leaves from a twig in order to slide it more easily into holes in termite mounds in order to "fish" for termites, which they eat. Since this act constituted modifying a natural object to make it more useful for a specific purpose, it qualified as tool-making. As far as I know, humans and chimpanzees are the only animals which make tools.
Also interesting is that chimpanzee tool-using behavior is not instinctive. Such behavior -- twig-stripping, using rocks to crack nuts, etc. -- occurs in some chimpanzee communities but not in others which have the same raw materials available on their territory, and it has been clearly observed that young chimpanzees learn it by observing older ones. In other words, chimpanzee tool use, like that of humans, is a form of culture.